Interpretive Summary: A naturally occurring virus (mosquito iridescent virus, MIV) that infects and kills mosquitoes that vector West Nile virus is being investigated by ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida in collaboration with cooperators in LaPlata Argentina at the Centro de Estudios Parasitológicos y Vectores. This is the first record of an MIV from Culex pipiens. This discovery will provide new biological and molecular information to investigate and understand basic mechanisms involved in infectivity and host range that will enhance capabilities to use these viruses for mosquito control.

Technical Abstract:
The mosquito iridescent viruses (MIVs) are large icosahedral DNA viruses that replicate and assemble in the cytoplasm of the host. Paracrystalline arrangements of virions that accumulate in the cytoplasm produce an iridescent color that is symptomatic of acute infections. In August 2010, we found larvae of Culex pipiens with these symptoms in suburban ditches around the city of La Plata, Argentina. Electron microscope studies, DNA sequencing, and phylogenetic analysis of the major capsid protein confirmed this as the first record of an MIV in C. pipiens.